Metal foil lead manufacture

ABSTRACT

A metal foil lead for sealing into vitreous material is comprised of a short length of metal foil ribbon having an etched tongue end portion with a feathered edge completely therearound and an unetched contact end portion. The foil leads may be made by forming a metal foil ribbon with slots in one side edge thereof at spaced points therealong, electrolytically etching the slotted side only of the ribbon to feather the exposed edges thereof, and then transversely severing the ribbon at each of the slots therein to separate it into individual foil leads.

United States Patent i g l 1451 Sept. 19, 1972 METAL FOIL LEADMANUFACTURE 3,571,899 3/1971 Sobieski ..29/412 [72] Inventor: ggrvey V.Siegel, Mayfield Heights, FOREIGN PATENTS OR APPLICATIONS 256,464 8 1926G tB 't ..76 105 [73] Assignee: General Electric Company rea n am I 22Filed; May 29 1969 Primary Examiner-John F. Campbell AssistantExaminer-Robert W. Church pp Nod ,863 Attorney-James J. Lazna, Henry P.Truesdell, Frank L. Neuhauser, Oscar B. Waddell and Melvin M. G01- 52us. Cl. ..29/25.l8, 29/418, 29/414, denberg 113/119, 204/142, 204/143 51Int. Cl ..H0lj 9/16 [57] ABSTRACT [58] Field of Search .....29/630, 629,25.18; 113/119; A metal foil lead for sealing into vitreous material is204/142, 143 comprised of a short length of metal foil ribbon having anetched tongue end portion with a feathered edge 5 References Citedcompletely therearoundand an unetched contact end portion. The foilleads may be made by forming a UNITED STATES PATENTS metal foil ribbonwith slots in one side edge thereof at spaced points therealong,electrolytically etching the Xg et a1 i2 slotted side only of the ribbonto feather the exposed 3414501 12 1968 K 4 142 X edges thereof, and thentransversely severing the rib- I ruger bon at each of the slots thereinto separate it into in- 3,43 l Lehner ..1 X dividual leads 3,484,53312/1969 Kauffman ..113/119 X 2,944,330 7/1960 Swick ..29/630 B 10Claims, 13 Drawing Figures PATENTED 8E! 19 I972 Inventor: Harvey V. Sieb9 gge L z OTTWEH METAL FOIL LEAD MANUFACTURE BACKGROUND OF THEINVENTION Field of the Invention This invention relates to metal foil orribbon leads, and to the manufacture of such leads, for sealing intovitreous envelopes of quartz or fused silica or of quartzlike hightemperature glasses, as in lamp manufacturmg.

In making a hermetic seal of a metallic conductor into a lamp envelopemade of fused quartz or a quartzlike glass such as 96 percent silicaglass, the very high temperatures required for softening and fusing thequartz restricts the choice of metals available for sealv ing thereintoin practice to molybdenum and tungsten both of which metals havecoefficients of expansion much greater, e.g., as much as ten timesgreater than quartz. To avoid cracking the quartz at the seal uponcooling, the lead-in conductor is shaped, at least over the hermeticallysealed portion thereof, as a thin ribbon or foil. The metal foil sealportionof the conductor, having become bonded to the quartz at arelatively high temperature, will merely go into tension withoutrupturing when the quartz cools, and cracking or shaling of the quartzat the seal is thereby avoided.

For effective sealing into quartz, the metal ribbon or foil should havea width to thickness ratio of at least about 100 to l, and in the caseof the thicker ribbons or foils they should taper down in thickness tothe sides at a taper angle not exceeding about 5 degrees to the edges.Metal ribbons or foils having such cross-sectional shape can be madeeither by longitudinally rolling a central portion of a length ofmolybdenum wire as described, for example, in US. Pat. No. 2,667,595,Noel et al, or by electrolytically etching a ribbon of metal foil. Thelongitudinally rolled onepiece molybdenum wire leads areparticularlysuitable for lower currents. For higher currents, or whereheavier electrodes or wire leads have to be supported by the metalribbons or foils during the sealing-in process, the etched metal foilsare preferred. Up to the present time, such etched metal foils havegenerally been produced by electrolytically etching a strip or ribbon ofthe metal foil of a few millimeters or so in width to feather the sideedges thereof, and then cutting the etched foil ribbon or strip intoindividual foil leads of the proper length required for the seal.Anouter wire lead, and either an inner wire lead or an electrode supportwire, are then welded to the opposite cut ends of each individual foillead to thereby form a complete welded ribbon lead-in conductor assemblyfor sealing into a quartz lamp envelope.

The cutting of the individual etched foil leads from the etched metalfoil strip or ribbon ordinarily leaves a burr along the cut edges ofeach metal foil lead. Owing to the fragility and comparatively smallsize of these thin metal foil leads, the removal of the burrs from theircut edges isa very difficult and impractical operation. The presence,however, of these burrs along the cut edges of the metal foil leads,together with the appreciable thickness of the metal foil along the cutedges, frequently causes thefailure of the seal, the fused quartzeventually cracking adjacent to the cut edges when the seal has cooleddown.

Another problem frequently encountered heretofore in the production ofetched metal foil leads with welded outer and inner wire leads orconductors is that in the welding of the wire leads to the'thin metalfoil, the foil is oftentimes burned completely through, therebyresulting in a defective weld. Also, the current-carrying capacity ofthe entire lead in conductor assembly is limited by that of the thinfoil immediately next to the weld. To help obviate these problems, ithas been customary, when making the weld of one or both the outer andinner leads to the metal foil lead, to thicken and thus reinforce themetal foil lead at the weld points thereof by the welding thereto ofsmall tabs of the metal foil material which are interposed between themetal foil lead and the wire leads at the respective weld pointsthereof. However, the cutting, handling and assembly of all thesevarious parts, together with the several welding operations required toform the completed lead-in conductor assembly, renders the fabricationthereof very complicated as well as costly. Moreover, the weld points ofthe inner and outer wire leads to the metal foil lead, and particularlythe outer wire lead weld point, frequently constitute a source ofpremature failure in the finished seals.

SUMMARY OF THE INVENTION IT is an object of the invention, therefore, toprovide aone-piece metal foil seal and outer lead only the seal portionof which is feather-edged therearound.

Another object of the invention is to provide a metal foil lead of novelconformation having an etched tongue portion at one end with a featherededge completely therearound and also having an unetched contact leadportion at its other end.

Still another object of the invention is to provide an electrical devicehaving a hermetic pinch seal in which is sealed a lead-in conductorwhich is comprised of an etched metal foil seal lead portion but whichis free of any outer weld between its seal and outer lead portions.

Afurther object of the invention is to provide a novel .method of makingthin metal foil leads having an etched tongue portion at one end with afeathered edge completely therearound and also having an unetchedcontact lead portion at its other end.

A still further object of the invention is to provide a process forforming metal foil leads of the type referred to above at a highproduction rate from a ribbon of metal foil.

Another object of the invention is to provide a continuous process forproducing metal foil leads of the type referred to above by forming aribbon of metal foil into an interconnected series of foil lead sectionswhich can be separated at the connecting regions into such individualmetal foil leads.

Briefly stated, in accordance with one aspect of the invention, the seallead and outer lead portions of the lead-in conductor assembly of anelectrical deviceare constituted by a single piece of metal foil ribbonhaving an etched tongue end provided with a feathered edge completelytherearound and serving as the seal lead portion of the lead-inconductor assembly, and an unetched contact end portion serving as theouter lead of the assembly.

In accordance with a further aspect of the invention, a strip or ribbonof thin metal foil such as molybdenum foil is first formed with narrowslots spaced along and extending transversely inward from one side edgeof the ribbon, after which the slotted side area only of the metal foilribbon is electrolytically etched to feather the exposed edges of theslotted side area of the ribbon including the edges of the slotstherein. The so-formed strip or ribbon is then transversely severed, asneeded, at each of the slots therein to separate it into individual foilleads.

Further objects and advantages of the invention will appear from thefollowing detailed description of a species thereof and from theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a fragmentary plan view of a strip or ribbon of metal foilwhich as been preformed in accordance with the invention with spacedslots in'one of its side edges for use in fabricating metal foil leadscomprising the invention;

FIG. 2 is a fragmentary plan view of the metal foil strip or ribbon ofFIG. 1 after it has been electrolytically etched in accordance with theinvention to feather the exposed edges of the slotted side area thereofincluding at least the outermost portions of the edges of the slotstherein;

FIGS. 3 and 4 are views similar to FIGS. 1 and 2 but showing amodification of the invention wherein protective etch-resist coatingsare applied onto localized areas of the metal foil strip adjacent theslotted edge thereof and between the slots therein prior to the etchingthereof but subsequently removed therefrom, as shown in FIG. 4;

FIG. 5 is a fragmentary plan view on an enlarged scale of a completedetched foil lead according to the invention formed by the severingthereof from the etched metal foil strip or ribbon of FIG. 2;

FIG. 6 is a sectional view on the line 6-6 of FIG. 5;

FIG. 7 is a sectional view on the line 7-7 of FIG. 5;

FIGS. 8, 9 and 10 are views corresponding to FIGS. 5, 6 and 7,respectively, and showing a metal foil lead out from theelectrolytically etched modified form of metal foil strip or ribbonshown in FIG. 4;

FIG. 11 is a perspective view of the etched foil lead shown in FIGS. 5to 7;

FIG. 12 is an elevation on an enlarged scale of an electric incandescentlamp provided with a foil seal and terminal structure according to theinvention; and

FIG. 13 is a diagrammatic view illustrating a continuous processaccording to the invention for forming a ribbon of metal foil into aseries of foil lead sections which may be subsequently separated fromone another by cutting to form individual foil leads comprising theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, thefoil lead 1 (FIG. 11) according to the invention is comprised of a shortlength 2 of thin metal foil ribbon such as, for example, molybdenum ortungsten foil having a thickness of, for instance, around 0.003 to 0.004inch, and having an etched tongue end or electrode portion 3 providedwith a feathered edge 4 completely therearound. The metal foil ribbon 2is of a length and width corresponding approximately to the length andwidth desired for the finished metal foil lead 1. For example, in theparticular case illustrated, the metal foil strip or ribbon 2 may have awidth of approximately one-fourth inch, and a length of around 1 inch orthereabouts. The other end portion 5 of the metal foil length 2 isunetched and serves as an outer lead or terminal contact for theelectric lamp or other electrical device into which the foil lead 1 isto be sealed. The outer end portion 5 of the foil lead is preferablyprovided, adjacent its outer end, with a locating aperture 6 of circularor other suitable shape, for use in fixing the location of the foil leadin the seal during the formation thereof.

As shown in FIG. 5, the etched tongue or inner end electrode portion 3of the foil lead 1 preferably is of generally pandurate or spade-shapedcontour in order to thereby provide a feathered edge 4 of extendedlength for sealing into the quartz or fused silica envelope of anelectric incandescent lamp or other electrical device. From the unetchedouter end portion 5 of the foil lead 1, the etched tongue end portion 3tapers gradually down in thickness to a sharp edge 4 aroundsubstantially its entire contour, as shown in FIGS. 6 and 7. For certainapplications, and especially for use with inner wire leads of largersizes that are to be welded to the etched tongue end portions of thefoil leads 1, the tongue end or electrode portion 3 may be formed at itstip end with a thicker end plateau welding area 7 on one or both sidesof the foil lead, as shown in the modified foil lead 1' in FIGS. 8 to10, the added foil thickness at the welding plateaus serving as anadditional protection against the burning through of the foil during thewelding of the wire lead to the foil lead.

In accordance with the invention, foil leads 1 of the constructiondescribed above and illustrated in FIGS. 5 to 11 may be producedeconomically and at high production rates by first forming a strip orribbon 8 (FIG. 1) of thin metal foil such as, for example, molybdenum ortungsten foil having a thickness of, for instance, around 0.003 to 0.004inch, with a series of spaced narrow slots 9 in one side edge 10 thereofso as to form the ribbon into a series of individual foil lead sections11. The other side edge 12 of the metal foil ribbon 8 is left unformedwith any such slots 9. As shown, the slots 9 extend transversely of thefoil ribbon 8, and they are spaced apart therealong a distance d(FIG. 1) corresponding approximately to the width desired for thefinished metal foil leads 1. The metal foil ribbon 8 is of a widthlikewise corresponding approximately to the length desired for thefinished metal foil leads 1. For example, in the particular caseillustrated, the metal foil ribbon 8 may have a width of approximately 1inch, and the slots 9 may be spaced apart a distance d of aroundone-fourth inch or thereabouts. The slots 9 themselves may have a widthof around one thirtysecond inch or so, and they extend inwardly of theribbon 8 from the edge 10 thereof a distance at least equal to thedesired length of the etched tongue end or electrode portions 3 of thefinished foil leads 1. In the particular case illustrated, wherein theetched tongue end portion 3 of the finished foil lead is of a lengtharound one-fourth to five-sixteenths inch, the slots 9 may extendinwardly from the edge 10 of the foil ribbon 8 a distance (aroundnine-sixteenths inch in the particular case illustrated) approximatelyequal to or slightly more than one-half the width of the ribbon 8.

As shown in FIG. l, the slots 9 are preferably widened for a shortportion of their length inwardly removed from the edge lid of the metalfoil ribbon b, as indicated at 13. The widened portions 13 of the slots9 may be formed by shallow U-shaped or approximately semicircular shapednotches, as shown, and they extend outwardly of the ribbon toward itsslotted side edge Ml, from the inner end of that portion of the lengthof each foil lead section lll which is to form the etched tongue endportion 3 of the finished foil lead 1, for a distance around half thelength or more of such tongue end portions 3 of the foil lead sectionsllll. As shown, the metal foil ribbon b may be also formed with a seriesof locating apertures s of circular or any other suitable shape adjacentits unslotted edge 12 and located approximately on the medial lines ofthe respective lead sections llll.

Where the modified form of metal foil leads ll shown in FIGS. 8 to W areto be formed, having the welding plateaus 7 at the outer tip ends of theetched tongue end portions 3 of the foil leads, the metal foil ribbon 8in such case is provided with discrete protective coatings M, as shownin FIG. 3, of a suitable etch-resist masking material applied to thoselocalized areas of the ribbon 8, adjacent the edge lltl thereof andbetween the successive slots 9 therein, which correspond to and are toform the welding plateaus 7 on the finished foil leads 1. Theseetch-resist protective masking coatings 14 may be applied either to bothsides of the metal foil ribbon 8 or to one side only thereof, orsuccessive ones of the coatings 14 may be applied onto alternatelyopposite sides only of the ribbon 8. The etch-resist protective maskingcoatings 14 may be applied either to both sides of the metal foil ribbon8 or to one side only thereof, or successive ones of the coatings 14 maybe applied onto alternately opposite sides only of the ribbon 8. Theetch-resist protective masking coatings 14 may be constituted of anysuitable material which will resist the etching action of the etchantmedium to which the metal foil ribbon 8 is to be subsequently subjectedduring the etching thereof. For example, where the metal foil ribbon 8is made of molybdenum and is to be subsequently etched in a sodiumhydroxide etching solution,the etch-resist protective coatings 14 insuch case may be composed of a material such as that commercially knownas black silicone rubber auto seal flexible adhesive sealantmanufactured by applicants assignee, which material is completelyresistant to any etching action thereon by the sodium hydroxide etchingsolution and which will therefore act to effectively mask the metal foilribbon 8 from the etching action of such an etching solution. Thematerial of which the etch-resist protective coatings 14 are constitutedshould be sufficiently adherent to the metal foil strip or ribbon 8 toremain firmly inplace thereon during the subsequent etching of theribbon.

The slotted metal foil strip or ribbon 8 of either FIG. 1, or of themodified form shown in FIG. 3 having the etch-resist coatings 14 appliedthereto, is then electrolytically etched over substantially its entirelength but throughout that slotted side area portion only of its widthwhich extends inwardly from the slotted edge to the line A-A (FIG. 1)and corresponds approximately to the length which the etched tongue endportions 3 are to have in the finished foil leads 1 or 1, to therebyfeather the exposed edges of such slotted side area portion of the metalfoil ribbon, including the edges 10 of the ribbon as well as the edgesof the slots 9 therein. The etching of the metal foil strip or ribbon 8may be conveniently carried out by immersing the slotted side area ofthe strip or ribbon 8 up to the etch line A-A (FlG. ll) in a bath 15(H0. H3) ofa suitable etching electrolyte such as, for instance, a 50percent solution of sodium hydroxide in the case where the metal foilstrip or ribbon 8 is constituted of molybdenum, which electrolyte bath15 is contained within an etching tank lit. The metal foil strip orribbon 8 is positioned in the electrolyte bath 115 between and inparallel relation to a pair of parallel extending copper bar typeelectrodes l7 and lb which are likewise immersed in the electrolyte bathand which are respectively connected, as by electrical conductors 19 and20, to the opposite sides of an AC. power source 21. The etching of themetal foil strip or ribbon d is continued until all the exposed edges ofthe tongue end portions 3 of the individual foil lead sections ill. ofthe strip or ribbon 8 are feathered to a sharp edge and the corners ofthe tongue end portions 3 are rounded off, as shown at 22 in FIGS. 2 andd. The length of time during which the metal foil strip or ribbon 8 mustbe subjected to the electrolytic etching action in order to accomplishthe above object will, of course, depend on various factors such as theamperage of the etching current applied to the electrodes 17, 18, thespacing of the metal foil strip or ribbon 8 from the electrodes 17, 18,the composition and temperature of the electrolyte 15 employed, and thecomposition and thickness as well as the partial width of the metal foilstrip or ribbon 8 to be etched. However, for a molybdenum metal foilstrip or ribbon 8 of approximately 0.003 inch thickness which is to beetched to a width of around one-fourth to five-sixteenths inch from itsedge 10 and which has its flat side surfaces spaced a distance of aroundone-half inch from the respective electrodes l7, l8, and with anelectrolyte 15 at room temperature and composed of a 50 percent solutionof sodium hydroxide, an etching time of approximately one to two minuteswith an etching current of around six amperes applied to the electrodes17, 18 ordinarily will suffice to accomplish the required degree ofetching of the metal foil strip or ribbon 8, as described above.

Etching is most rapid at the edges of the tongue end portions 3 of thefoil lead sections 11 of the strip or ribbon 8 and is a maximum at thecomers thereof. This causes the corners to become rounded as indicatedat 22 in FIGS. 2 and 4, and the edges to become feathered to a sharpedge, as illustrated at. 4 in FIGS. 6 and 7. However, etching takesplace all over the tongue end portions 3 of the metal strip or ribbon 8which are immersed in the electrolyte 15. In the case of the modifiedform of metal foil strip or ribbon 8 of FIG. 3, however, whereinetch-resist protective coatings 14 are provided on localized areas ofthe tip ends of each of the tongue end portions 3 of the metal foilstrip or ribbon 8, etching takes place over all the tongue end portions3 except in the areas masked off by the etch-resist protective coatings14 where the etching electrolyte does not have access to the metal foil.This results in thicker localized areas or plateaus 7 (FIG. 4) at thetip ends of each foil lead section 11 of the metal foil strip or ribbon8, where the etch-resist protective coatings 14 mask off such areas ofthe ribbon, these thicker plateau areas 7 remaining at the originalthickness of the metal foil strip or ribbon 8, in the case where themasking coatings 14 are applied to both sides of the metal foil strip orribbon 8 but being reduced to a thickness somewhere around three-fourthsthat of the original foil thickness in the case where the maskingcoatings 14 are applied to one side only of the metal foil strip orribbon 8. From the thicker end plateau areas 7 on the etched tongue endportions 3 of the modified form of etched metal foil ribbon 8 shown inFIG. 4, the foil thickness tapers down to that of the adjacent etchedcentral and side areas 23 and 24, respectively, of the tongue endportions 3, as shown in FIGS. 9 and 10. Along the medial center line ofthe etched tongue end portion 3 of each foil lead section 11, thethickness in the central region 23 thereof may be around half or lessthan half the original thickness of the metal foil prior to the etchingthereof. Thus, where the original foil thickness was in the range of0.003 to 0.004 inches, the thickness along the medial line of eachtongue end portion 3 at its central region 23 after etching may bearound 0.001 inch. The thickness of the tongue end portion 3 of eachfoil lead section 11 tapers transversely thereof to zero at the edges,as shown at 4 in FIGS. 6 and 9.

Upon completion of the etching operation, the etched metal foil strip orribbon 8 is withdrawn from the electrolyte bath l and, in the case ofthe modified form of etched foil strip or ribbon 8 of H6. 4, theprotective masking coatings 14 then stripped off the ribbon 8 in asuitable manner as, for example, by scraping the coatings 14 off theribbon 8 with a stripper knife. Any remaining electrolyte on the stripor ribbon 8 is then removed therefrom in a suitable manner, as bywashing it off either by directing a water spray 25 against the oppositeflat sides of the strip or ribbon 8 from spray nozzles 26 (FIG. 13), orby immersing the metal foil strip or ribbon 8 in a water rinse bath.Preferably, however, the remaining etching electrolyte on the metal foilstrip or ribbon 8 is removed therefrom by first immersing the ribbon ina neutralizing acid bath 27 (FIG. 13) contained in a tank 28 to causethe remaining sodium hydroxide etchant, which is a base, to react withthe acid to form a salt, and then washing off the resulting reactionproduct along with any acid or other foreign material remaining on thestrip or ribbon 8 in a suitable manner, preferably by directing a waterspray 25 from the nozzles 26 against the opposite flat sides of thestrip or ribbon 8, followed by immersion thereof in an alcohol rinsebath contained in a tank (not shown), the alcohol absorbing any of therinse water remaining on the strip or ribbon 8 and being easier to dryoff the strip or ribbon than the water alone.

The resulting metal foil strip or ribbon 8 (FIGS. 2 and 4) which isformed by the above-described processing operations, and which iscomprised of a series of foil lead sections 11 having etched tongue endportions 3 of the feathered edge form and shape described hereinaboveand joined together at their outer contact end portions 5 (FIGS. 2 and4) along the unslotted side or edge 12 of the ribbon, is thentransversely severed at each of the slots 9 therein, along the cuttinglines 29 as shown in FIG. 2, to thereby separate the strip or ribbon 8into individual foil leads 1 or 1' (FIGS. 5 to 11) each having an etchedfeather-edged tongue portion 3 for welding thereto of the inner wirelead 30 of a filament mount 31, as shown in FIG. 12, and subsequentsealing thereof into a quartz envelope of an electric lamp in the mannercustomary in the lamp making art. In the case of foil leads 1' of themodified form shown in FIGS. 8 to 10, having the welding plateaus 7 atthe tip ends of their etched tongue end portions 3, the added thicknessof the metal foil at the welding plateaus 7 serves as an additionalsafeguard against the burning through of the foil during the welding ofthe inner wire lead 30 to the foil lead 1 While the above-describedmethod according to the invention for making foil leads 1 or 1' of thetype shown in FIGS. 5 to 11 may be practiced as a batch process whereinindividual metal foil strips 8 of determinate length are formed to thedesired foil lead shaped sections 11 as shown in FIGS. 2 and 4 and thenlater cut into individual foil leads 1 or 1, or the foil lead sections11 instead cut from the metal foil ribbon 8 prior to the etching thereofand then individually etched to form the finished foil leads 1 or 1, itis preferable to practice the described method as a continuous processas shown in FIG. 13 wherein the metal foil strip or ribbon 8 to beprocessed is in the form of a continuous ribbon thereof which may becontained on a supply spool 32. The continuous ribbon 8 of metal foil onthe supply spool 32 may be either preformed with the spaced slots 9(FIGS. 1 and 3), or it may be of plain form unprovided with such slots.Where the supply of metal foil ribbon 8 on the spool 32 is of plainunslotted form, it is withdrawn from the spool 32 and guided intosuitable means such as a slotting punch (not shown) which punches thespaced slots 9 in the side edge 10 of the ribbon 8. The slottedcontinuous ribbon 8 of metal foil is then passed, with its slotted edge10 facing downwardly, through the etching electrolyte bath 15 in thetank 16 (as by passing the ribbon through suitable liquid-tight seals 33in the side walls of the tank) and between and in parallel relation tothe parallel extending copper bar electrodes l7, 18 therein, which areelectrically connected by the conductors 19, 20 to an A.C. power supply21, to thereby effect the electrolytic etching of the advancing metalfoil ribbon 8 to the desired final configuration thereof as shown anddescribed above in connection with FIGS. 2 and 4. During its passagethrough the etching tank 16, only the slotted sideedge 10 of the metalfoil ribbon 8 is immersed in the electrolyte bath 15 up tothe desiredetching line A-A (FIG. 1) of the ribbon. The rate of movement of themetal foil ribbon 8 through the etching electrolyte bath l5 and theetching time thereof is so adjusted, in relation to the other etchingrate control factors such as the etching current, the composition andtemperature of the etching electrolyte l5, and the composition,thickness and width of the metal foil ribbon 8 and the spacing thereoffrom the respective electrodes 17, 18, as to effect the required degreeof etching of the metal foil ribbon, as described hereinbefore.

From the etching tank 16, the continuous ribbon 8 of metal foil is thenpassed through a neutralizing acid bath 27 in a tank 28, throughsuitable liquid-tight seals 33 therein, to cause any of the causticalkali electrolyte 15 (e.g., sodium hydroxide solution) remaining on theribbon to react with the acid to form a salt. From the neutralizing acidbath 27, the ribbon 8 is then guided past water sprays 25 directedagainst the opposite flat sides of the ribbon by spray nozzles 26 towash off the reaction product of the neutralizing acid 27 andelectrolyte 15 as well as any excess acid remaining on the ribbon 8. Thewashed ribbon 8 may then be passed, if desired, through an alcohol rinsebath (not shown) to cause absorption by the alcohol of any rinse waterremaining on the ribbon 8, and then guided past a pair of air jets 34directed against the opposite flat sides of the ribbon 8 by a pair ofair nozzles 35 to effect the thorough drying of the ribbon. The driedmetal foil ribbon 8 then may either be wound onto a take-up spool 36,which may be suitably rotated to effect the withdrawal of theribbon 8off the supply spool 32 and its advance movement through the tanks 16and 28, for subsequent severing of the coiled ribbon 8 into individualfoil leads 1 or 1', as needed, or the processed ribbon 8 may be fed by apair of suitable feed rolls (not shown) to a severing mechanism 37comprising, for example, a stationary bed knife 38 and a movableshearing knife 39, for cutting the ribbon 8 along the transverse cuttinglines 29 (FIG. 2) into individual foil leads 1 or 1'.

The above-described continuous process according to the invention forfabricating a shaped metal foil ribbon 8 of the configuration as shownand described in connection with FIGS. 2 and 4 and subsequently severingthe shaped ribbon 8 into individual foil leads 1 or 1' of the typeillustrated in FIGS. to 11, is of particular advantage for the reasonthat the continued advance movement or travel of the metal foil ribbon 8through the etching electrolyte bath l5 acts to break up the bubbleswhich ordinarily tend to form in the etching electrolyte solution duringthe etching operation and which would partially block the passage of theetching current through the electrolyte and so cause a variation in therate of etching and therefore the degree of etching of the metal foilribbon. The breaking up of the bubbles in the etching electrolyte l5assures a more uniform current flow through the etching electrolyte atall times during the etching operation, and thus a more uniform rate ofetching of the metal foil ribbon 8. Consequently, greaterreproducibility of results in the shape and form of the etched metalfoil ribbon 8 and in the individual foil leads 1 or 1 to be cuttherefrom is afforded by the continuous process according to theinvention. In addition, the movement of the metal foil ribbon 8 throughthe etching electrolyte solution 15 acts to minimize the heating of theelectrolyte by the etching current passing therethrough as well as toassure the uniform heating of the electrolyte. Since the etchingelectrolyte solution 15 becomes more reactive and it's etchingrateincreases the higher its temperature, the minimization of the heating ofthe electrolyte by the etching current and the maintenance thereof morenearly at a uniform temperature during the etching operation, whichconditions are inherent in the continuous process as described above,therefore likewise assures greater reproducibility and uniformity ofresults in the shape and form of the etched metal foil ribbon 8 and thefoil leads 1 or 1' which are subsequently cut therefrom.

FIG. 12 illustrates an electrical device, for example, an electricincandescent lamp 40 of the well known tungsten-halogen regenerativecycle type, provided with a lead-in conductor assembly and sealaccording to the invention. As there shown, the particular lamp 40illustrated comprises a tubular envelope 41 of quartz or quartz-likeglass formed at its opposite ends with conventional type flattened pinchseals 42 into each of which is sealed the etched feather-edged tongueend portion 3 of a foil lead 1 m1 of the type acv cording to theinvention and having an inner wire lead 30 welded to the tip end of itstongue end portion 3. As shown, the foil leads 1 or 1' are sealed intothe pinch seals 42 with their etched flat tongue end portions 3projecting into and disposed flatwise within and embedded in theflattened pinch seals 42 and with their unetched contact end portions 5projecting endwise from the envelope outwardly from the outer ends ofthe pinch seals 42 to thereby serve as the terminal contacts for thelamp. Disposed within the envelope 41 is a tungsten filament 43, forexample, a linear coil or coiledcoil of tungsten wire disposed more orless axially within the tubular envelope 41, which is electricallyconnected at its opposite ends in a suitable manner, as by means ofconnecting spud wires 44 for instance, to the inner wire leads 30 weldedto respective ones of the metal foil leads 1 or 1'. The envelope 41 alsocontains a filling of inert gas such as argon plus a small amount of ahalogen such as iodine or bromine or compounds thereof, as is well knownin the art, the envelope 41 being exhausted and the gas fillingintroduced thereinto through an exhaust tube 45 which is then tipped offas indicated at 46. In manufacturing such a lamp 40, the filament 43 isfirst connected at its opposite ends, as by means of the connecting spudwires 44, to the inner wire leads 30 of respective foil leads I or 1' toform a lamp mount assembly 31 which is then inserted into the tubularenvelope 41 and held in proper sealing position therein while the pinchseals 42 are formed at the opposite ends of the envelope, and the gasfilling introduced thereinto and the exhaust tube tipped off, all in themanner customary in the art. During this scalingin of the lamp mountassembly 31. into the envelope 4], the lamp mount assembly may beaccurately held in place therewithin by suitable jig means (not shown)engaging with the locating apertures 6 of the foil leads 1 or 1',thereby enabling the fabrication of lamps with uniformly centered andaligned filaments 43 within the lamp envelope 41. If desired, asupplemental metal base or lug 47, as shown in dotted lines in FIG. 12,may be suitably fastened to the projecting outer end portions 5 of eachof the foil leads 1 or 1', as by welding or clamping for example, tothereby serve as the terminal contact members for the lamp.

Metal foil leads 1 or 1' of the type comprising the invention are mucheasier and considerably less expenemploying metal foil leads accordingto the invention because of the absence of any such outer weld. Longerlamp life is thereby afforded by the use of metal foil leads 1 or 1'comprising the invention. Moreover, seals employing metal foil leads 1or 1' according to the invention can be safely operated at temperatureswell above 300C, such as are encountered in lamps designed to operate athigh current ratings, without the likelihood of the seal failing due tocorrosion of the lead. By way of contrast thereto, such high sealtemperature operation is not feasible with seals employing rolled wireribbon leads because of the susceptibility of such leads to corrosion atsuch elevated seal temperatures.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of making thin metal foil leads for sealing into vitreousmaterial which comprises the steps of forming a flat ribbon of metalfoil having slots in one side edge thereof at spaced points therealong,electrolytically etching the slotted side area only of the said flatmetal foil ribbon to feather the exposed edges of said slotted foil areato a sharp edge, and then severing the etched flat metal foil ribbontransversely of its length at each of the said slots therein to separatethe ribbon into individual flat metal foil leads each comprised of anetched tongue end foil portion having feathered edges completelytherearound and an unetched contact end foil portion.

2. The method as specified in claim 1 wherein the said slots in themetal foil ribbon are formed with widened inner portions.

3. The method as specified in claim 1 wherein the said metal foil ribbonconsists of molybdenum.

4. The method as specified in claim 1 wherein the said ribbon of metalfoil is of continuous form and the said electrolytic etching of theribbon is effected by longitudinal passage of the said slotted side areaonly thereof through an etching electrolyte between and in spacedparallel relation to a pair of elongated spaced electrodes disposedwithin the electrolyte and electrically connected to respective sides ofan A.C. power supply.

5. The method of making thin metal foil leads for sealing into vitreousmaterial which comprises the steps of forming a flat ribbon of metalfoil having slots in one side edge thereof at spaced points therealongand ap-' plying discrete protective coatings of an etch-resist maskingmaterial on at least one side of the said flat metal foil ribbon overlocalized areas thereof at its slotted side edge and between adjacentones of the said slots therein, electrolytically etching the slottedside area only of the said flat metal foil ribbon to feather the exposededges of said slotted foil area to a sharp edge, removing the saidprotective coatings from the metal foil ribbon, and then severing theetched flat metal foil etchi rgg1 of the ribbon.

6. e method of preparing a continuous flat ribbon of metal foil forsubsequent separation into individual flat foil leads having featherededges at one end only thereof which comprises the steps of forming aflat ribbon of metal foil having slots in one side edge thereof atspaced points therealong, and then electrolytically etching the slottedside area only of the said flat metal foil ribbon to feather the exposededges of said slotted foil area to a sharp edge.

7. The method as specified in claim 6 wherein discrete protectivecoatings of an etch-resist masking material are applied on at least oneside of the metal foil ribbon, prior to the said etching thereof, overlocalized areas of the ribbon at its slotted side edge and betweenadjacent ones of the said slots therein, and the said protectivecoatings then removed from the metal foil ribbon after the said etchingthereof.

8. The method as specified in claim 6 wherein the said electrolyticetching of the said metal foil ribbon is effected by longitudinalpassage of the said slotted side area only of the ribbon through anetching electrolyte between and in spaced parallel relation to a pair ofelongated spaced electrodes disposed within the electrolyte andelectrically connected to respective sides of an A.C. power supply.

9. The method as specified in claim 8 wherein discrete protectivecoatings of an etch-resist masking material are applied on at least oneside of the metal foil ribbon, prior to the said etching thereof, overlocal ized areas of the ribbon at its slotted side edge and betweenadjacent ones of the said slots therein, and the said protectivecoatings then removed from the metal foil ribbon after the said etchingthereof.

10. The method of making thin metal foil leads for sealing into vitreousmaterial which comprises the steps of forming spaced arcuate slots onone longitudinal edge of a metal foil strip leaving electrode portionsfreely extending therefrom, each said electrode portion configured todefine an enlarged free end portion and a necked down intermediateportion, etch resist masking a portion of the surface area of the saidenlarged free end portions of said electrode portions and leaving thesaid necked down portions thereof exposed, feathering theexposed'portions of said electrode portions to a sharp edge byelectrolytically etching the said portions, and then forming thecompleted foil leads by transversely separating the said foil strip ateach of said slots.

1. The method of making thin metal foil leads for sealing into vitreousmaterial which comprises the steps of forming a flat ribbon of metalfoil having slots in one side edge thereof at spaced points therealong,electrolytically etching the slotted side area only of the said flatmetal foil ribbon to feather the exposed edges of said slotted foil areato a sharp edge, and then severing the etched flat metal foil ribbontransversely of its length at each of the said slots therein to separatethe ribbon into individual flat metal foil leads each comprised of anetched tongue end foil portion having feathered edges completelytherearound and an unetched contact end foil portion.
 2. The method asspecified in claim 1 wherein the said slots in the metal foil ribbon areformed with widened inner portions.
 3. The method as specified in claim1 wherein the said metal foil ribbon consists of molybdenum.
 4. Themethod as specified in claim 1 wherein the said ribbon of metal foil isof continuous form and the said electrolytic etching of the ribbon iseffected by longitudinal passage of the said slotted side area onlythereof through an etching electrolyte between and in spaced parallelrelation to a pair of elongated spaced electrodes disposed within theelectrolyte and electrically connected to respective sides of an A.C.power supply.
 5. The method of making thin metal foil leads for sealinginto vitreous material which comprises the steps of forming a flatribbon of metal foil having slots in one side edge thereof at spacedpoints therealong and applying discrete protective coatings of anetch-resist masking material on at least one side of the said flat metalfoil ribbon over localized areas thereof at its slotted side edge andbetween adjacent ones of the said slots therein, electrolyticallyetching the slotted side area only of the said flat metal foil ribbon tofeather the exposed edges of said slotted foil area to a sharp edge,removing the said protective coatings from the metal foil ribbon, andthen severing the etched flat metal foil ribbon transversely of itslength at each of the said slots therein to separate the ribbon intoindividual flat metal foil leads each comprised of an unetched contactend foil portion and an etched tongue end foil portion having featherededges completely therearound except for the unetched end plateau areasof the foil leads masked off by the said etch-resist protective coatingsduring the etching of the ribbon.
 6. The method of preparing acontinuous flat ribbon of metal foil for subsequent separation intoindividual flat foil leads having feathered edges at one end onlythereof which comprises the steps of forming a flat ribbon of metal foilhaving slots in one side edge thereof at spaced points therealong, andthen electrolytically etching the slotted side area only of the saidflat metal foil ribbon to feather the exposed edges of said slotted foilarea to a sharp edge.
 7. The method as specified in claim 6 whereindiscrete protective coatings of an etch-resist masking material areapplied on at least one side of the metal foil ribbon, prior to the saidetching thereof, over localized areas of the ribbon at its slotted sideedge and between adjacent ones of the said slots therein, and the saidprotective coatings then removed from the metal foil ribbon after thesaid etching thereof.
 8. The method as specified in claim 6 wherein thesaid electrolytic etching of the said metal foil ribbon is effected bylongitudiNal passage of the said slotted side area only of the ribbonthrough an etching electrolyte between and in spaced parallel relationto a pair of elongated spaced electrodes disposed within the electrolyteand electrically connected to respective sides of an A.C. power supply.9. The method as specified in claim 8 wherein discrete protectivecoatings of an etch-resist masking material are applied on at least oneside of the metal foil ribbon, prior to the said etching thereof, overlocalized areas of the ribbon at its slotted side edge and betweenadjacent ones of the said slots therein, and the said protectivecoatings then removed from the metal foil ribbon after the said etchingthereof.
 10. The method of making thin metal foil leads for sealing intovitreous material which comprises the steps of forming spaced arcuateslots on one longitudinal edge of a metal foil strip leaving electrodeportions freely extending therefrom, each said electrode portionconfigured to define an enlarged free end portion and a necked downintermediate portion, etch resist masking a portion of the surface areaof the said enlarged free end portions of said electrode portions andleaving the said necked down portions thereof exposed, feathering theexposed portions of said electrode portions to a sharp edge byelectrolytically etching the said portions, and then forming thecompleted foil leads by transversely separating the said foil strip ateach of said slots.